The invention relates to a device for activating a security system in a vehicle at least two vehicle sensors (4), each of which can record vibrations in frequency ranges, which are generated both by an acceleration and by structure-borne noise, and which comprise in each case at least one measuring value sensor (4.1) for recording vibrations, and a central unit (2) which evaluates the signals from the vehicle sensors (4), and which activates the security system according to said signals, and a related procedure for activating a security system in a vehicle with at least two vehicle sensors (4), which record the vibrations in frequency ranges which are generated both by an acceleration and by structure-borne noise, and which comprises in each case at least one measuring value sensor (4.1) to record vibrations, and a central unit (2) which evaluates the sensor signals from the vehicle signals, and which activates the security system according to said signals.
Vehicle security systems require sensors to record the each driving or accident situation in order to react in an appropriate way. It is known that measuring value sensors can be used as crash sensors in order to record the acceleration and structure-borne noise. An impact with an obstacle or a collision with an obstacle is detected by the evaluation of the measured acceleration and the measured structure-borne noise, and safety measures are initiated by the security system accordingly. Determining the origin of an impact is of great importance in order to improve the use of security systems such as airbags, belt tighteners or pedestrian protection systems.
Sensors known to date which are used to record the structure-borne noise are designed to record preferably transverse structure-borne noise waves. Since no one individual sensor of this type is capable of determining the direction of dissemination of a transverse structure-borne noise wave, several sensors must be linked in order to determine the location of the source of the structure-borne noise wave, and in part, the evaluation of the measured structure-borne noise values involves, in part, extensive and complex calculations.
Sensors to record the acceleration and the structure-borne noise have a further, decisive disadvantage. Their direction of sensitivity for recording the structure-borne noise is often not the same as the direction of sensitivity for recording the acceleration. For this reason, more than two sensors frequently have to be provided to determine the impact location of the obstacle in order to guarantee that the security system will be activated in a manner appropriate to the accident.
A control device for a security system is known from DE 100 15 273 A1, in which four sensors for recording the acceleration and structure-borne noise are provided, which are arranged in such a manner that each sensor comprises a different direction of sensitivity. In this way, it is not only possible to determine the direction of the acceleration, but also be determine faults in the sensors.